Sampling results from the fifth round of Friends of the Mad River’s Mad River Watch (MRW) program show one site with unfavorable swimming conditions as of Monday morning, August 8.
Lareau swim hole in Waitsfield results show 410 colonies of E. coli per 100 ml of water, well over the Vermont Department of Health/Environmental Protection Agency accepted “swimmable” E. coli level of 235 colonies per 100 ml of water. It is estimated that at the level of 235 colonies E.coli per 100 ml water, approximately eight out of every 1,000 swimmers are likely to contract a waterborne illness related to fecal contamination.
While the cause of this elevated E. coli is currently unknown, it may be due to people’s concentrated use of this site. It may also be due to contamination in the sampling or lab process. Encourage fellow Lareau swim hole visitors to be good stewards of the water and use the porta-john and trash receptacles provided on the site, for the benefit of all.
This is the first site recorded above 235 colonies per 100 ml of water this season. While this can be seen as positive news for the swimmers among us, consistently low E. coli levels don’t necessarily indicate a watershed without pollutants. In this case, they’re more of an indication of the dry weather patterns this summer and the resulting low river flow around MRW sampling days.
Rains carry sediments, nutrients and pathogens from the land and into the river and streams, increasing E. coli levels (among other pollutant levels). During dry weather, the pollutants don’t reach waterways. After over a week without substantial rain, the flow condition of the Mad River at the time of sampling Monday morning was low and steady (LS) and flowing at 25 cubic feet per second (cfs) at the USGS flow gage in Moretown, lower even than its median for this date of 103 cfs.
“Friends of the Mad River’s E. coli sampling results are only a snapshot in time intended to give you a sense of the conditions that lead to high pathogen levels in the water so you can be informed. This weekend looks to be a wet one, so you and your good judgment are your best protector – use common sense and don't swim for at least 24 hours after a rain,” said Corrie Miller, executive director of Friends of the Mad River.
This week’s Mad River Watch volunteers were Charlie Baldwin, Richard Czaplinski, Susy Deane, Chase Fortier, Kinny Perot, Fran and Gary Plewak and Michael Ware. Susanne and George Schaefer drove water samples to the lab in Burlington for phosphorus, nitrogen and turbidity analysis and Sally Boudreau posted data at swim holes across the watershed. Paula Baldwin is the lab coordinator.
For more information about E. coli and the Mad River Watch program and to view the most recent complete data report visit the Friends of the Mad River website at www.FriendsoftheMadRiver.org.